Telephone



(No Model.)

C. I'. DUNDBRDALE.

TELEPHONE.

No. 666,496. Patented M6151?, 1896.

UNITED STATES PATENT OFFICE.

CLEAVELAND F. DUNDERDALE, OF CHICAGO, ILLINOIS, ASSIGNOR TO TIIE AUTOMATIC LONG DISTANCE TELEPHONE COMPANY, OF ILLINOIS.

TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 556,496, dated March 17, 1896.

Application filed May Zl, 1895. Serial No. 550,472. (No model.)

To all wtont it may concern.-

Be it known that I, CLEAVELAND F. DUN-l` DERDALE, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Telephones, of which the following is a specification.

My invention relates Ato that class of telephones in which the variable-resistance medium consists of interposed granulated or comminuted conducting material, the mass of which is influenced or varied by the action of the diaphragm under the sound-waves. In the action of this type of telephone it is known that by placing a piece of loose carbon, free from any mechanical pressure or tension other than its own mass, between a diaphragm of suitable material acting as an electrode for the passage of the current and another electrode positioned adjacent thereto, that any vibrations or molecular disturbances of the diaphragm-electrode will be communicated to the piece of loose carbon, causing it to respond sympathetically in movement to the movement of the diaphragm and produce a variation `of current strength between the diaphragm and the adjacent electrode. It is also known that in the absence of some other mechanical action than the mass of the loose piece of carbon or a break-piece to control the movement thereof its movement will not be responsive perfectly to the movements of the diaphragm, and consequently that the variation in resistance and variation in current strength will not be in perfect accord with the movements of the sound-waves impactin g upon the diaphragm. This imperfect response to the movements of the diaphragm produces the rattling or grating sounds which are heard in the receiver and which, therefore, greatlyimpair the distinctness of the vocal or musical sounds. To overcome this defect resorthas hitherto been had to extraneous pressure, in some instances springs being provided acting on the loose piece of carbon constituting the intermediate movable electrode and by thus holding the latter suppress the increased or multiplied movement of the same and reduce it to a movement synchronous with that of the diaphragm. These extraneous means have been found to injuriously affect the timbre of vocal or musical sounds. In order to overcome those peculiar sounds produced in the transmitter which tend to confuse the reproduced sound due to the 5 5 arcing of the current in different degrees at the several points of Contact, and also to overcome the burning out of contacts, carbon transmitters in which the carbon is granulated are employed, but at the expense of the 6o strength or loudness of the sound transmitted.

The object of my invention is to secure the full advantage of a maximum current strength or loudness of sound transmission, and also those advantages whereby a larger amount of current may be employed without injurious arcing or the production of confusing sounds, so that the sound-waves may be transmitted for greater distances.

My invention has certain other objects in 7o View; and it consists in certain features to be described and particularly pointed out in my claims, reference being had to the accompanying drawings, in which- Figure 1 is a sectional View of complete in- 75 strument. Fig. 2 is aplan view with the cap removed. Fig. 3 is a sectional View of a modiiied form.

In carrying out my invention I preferably employ a diaphragm 5 of carbon, which is So held between the box 6 and the cap or cover 7 carrying the mouthpiece 8 and screwed upon the box 6. To the diaphragm 5 a circuit-lead 9 is connected, the other lead, 10, of which circuit is connected to the conducting-screw 11 8 5 which passes through or partially through the lblock of carbon 12 held in the box 6 by said screw 1l in a position adjacent to the diaphragm 5. The diaphragm 5 therefore'constitutes a movable electrode and the block of 9o carbon 12 a xed electrode adjacent to the movable electrode.

The intermediate movable electrode consists, as shown in Figsl and 2, of apluralityof small spheres of carbon or other high-,resistance and consequently low-conducting material, (designated at 13,) which are disposed within the recesses or depressions 14 in the fixed electrode 12. Those surfaces of the spheres 13 opposite to the portions thereof roo within the recesses 14 are in close proximity to the diaphragm when the instrument is in a horizontal plane, as shown in Fig. l, so that when the instrument is placed in a vertical position the spheres 13 partially move outward from within the recesses 14 and contact against the diaphragm 5, these spheres 13, however, having a free movement in and out of the recesses 14 under the inucnce of the movements of the diaphragm 5.

Vithn the space between the diaphragm 5 and the fixed electrode 12 I place a quantity of granulated or comminuted carbon, (designated at 15,) which completelysurrounds these movable spheres 13 and are interspersed between the diaphragm 5 and the fixed electrode 12. By this arrangement the mass of comminuted carbon and the spheres are caused to move in unison in response to the move ment of the diaphragm under the influence of the sound-waves, and together with the spheres provide a free intermediate movable electrode capable of establishing delicate variations of resistance and at the saine time overcome any arcing of the electric current by absorption, and by the cohesive gravity of the mass of comminuted carbon surrounding such spheres act as a delicate tension-regu lator, exerting a restrictive pressure upon the naturally too free movement of such spheres, thus preventing confusing sounds and providing a perfect sympathetic synchronous fiow of electric current in exact response to the sound-waves imparting movement to the diaphragm.

It is evident that the spheres 13 may be made in some other form without departing from the spirit of my invention, or the spheres or other bodies instead of being placed in the recesses 14: may be left free to move in every direction.

It willbe understood that the current passes from the diaphragm through the mass of comminuted carbon and the spheres of carbon.

Instead of the movable spheres of carbon or carbon pieces of other form free to move about I may employ the form shown in Fig. 3, in which the fixed electrode 12 has projected from its inner face a plurality of fixed studs, a mass of comminuted carbon constituting the high-resistance conductor being disposed between the fixed electrode 12 and the diaphragm 5, this carbon in a comminuted state being interspersed about the studs 1G.

XVhenever the term conducting material is employed throughout the specification and claims I do not desire to be understood as having limited myself of necessity to the use ,of materials commonly designated as con ductors or non-conductors, but I desire to be understood as employing this term to designate any kind or character of material which may be suitable as a variableaesistance medium through which the current passes.

Having thus described my invention, what I claim as new therein, and desire to secure by Letters Patent, is

1. In a telephone a diaphragm constituting one electrode a back piece in proximity to the diaphragm, a conducting-body or conducting-bodies disposed between the electrodes aforesaid and a mass or quantity of comminuted or granulated conducting material surrounding the conducting-bodies aforesaid.

2. In a telephone a diaphragm constituting one electrode, another electrode in proximity thereto having sockets or recesses therein a conducting-body or conducting-bodies partially within said pockets or recesses and a mass or quantity of comminuted or granulated conducting material disposed above the conducting-bodies aforesaid.

3. In a telephone the combination with the diaphragm of a back piece in proximity thereto constituting the other electrode, a conducting-body or conducting-bodies adapted to move freely between the electrode and a mass or quantity of granulated or comminuted conducting material surrounding the conducting-bodies aforesaid and operating to control the movement of t-he said bodies the said comminuted or granulated conducting material and the conducting-bodies serving to provide a variable-resistance medium between the two electrodes.

4. In a telephone the combination with the diaphragm constituting an electrode of aback plate constituting another electrode opposite and in proximity to the diaphragm, an interposed body or bodies of high resistance and low conductivity within the space between the said electrodes and a quantity of like material in a granulated or comminuted state surrounding said bodies and operating as a tension-regulator therefor.

5. In a telephone the combination with the diaphragm constituting an electrode of a back plate also constituting an electrode, studs of high-resistance conducting material project ed from the back plate, an interposed body or bodies of high resistance and low conductivity within the space between the said electrodes and a quantity of like material in a granulated or comminuted state surrounding said bodies and studs operating as a tensionregulator therefor.

In testimony whereof I affix my signa-turc in presence of two witnesses.

CLEAVELAND F. l)Ul\'llfllRD,l\ljli.

Witnesses C. C. BULKLEY, W. T. ToMPxINs.

IOO

IIO

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